Out of band signaling systems are vastly utilized for telephony setup. The out of band signaling is separated from the channel carrying the information. Thus, the signaling and control information does not intrude upon the media channel. SS7 (Signaling System 7) is a typical out of band signaling protocol utilized for telephony networks in North America. C7 is a protocol in Europe, equivalent loosely to SS7.
Due to the rapid development of Internet technologies, voice communications via the Internet using Voice over Internet Protocol (VoIP) has become a practical and cost-saving solution instead of, or in combination with, traditional telephony networks. H.323 is a standard widely accepted for implementing voice communications (and other real-time multimedia communications) over a packet switched data network (such as the Internet). H.323 governs allocation of call resources, call tear down, management of gateway resources, and other functions required on the packet switched data network.
A typical combination of a telephony network and a packet switched data network is a system shown in FIG. 1, which implements phone-to-phone calls. Different from traditional telephony systems, the system shown in FIG. 1 comprises three network legs. Both the origination and termination legs are traditional telephony networks (such as PSTN) while the middle leg is Internet bridging between the origination and termination legs. In the origination leg, a call is initiated by a calling device or telephone 110 and transmitted to an origination gateway 116 of IP network 107 through switches 112 and 114 of the PSTN network 103. In the middle leg, the call is transmitted from the origination gateway 116 to termination gateway 118 over IP network 107 according to the VoIP protocol. In the termination leg, the call is finally transferred from the termination gateway 118 through the switches 124 and 128 of PSTN network 105 to the called device or telephone 130. It can be appreciated that costs, especially for long distance calls and international calls, can be dramatically decreased because the two PSTNs are interconnected by the Internet.
However, a drawback exists in the call setup process in such a combination system. As shown in FIG. 1, first an out of band signaling (e.g., SS7) takes place on the origination leg. Then, H.323 signaling takes place in the middle leg, allocating the use of resources in the IP network, and transmitting the call setup information to the termination leg. Finally, SS7 signaling takes place in the terminal leg. Therefore, the H. 323 signaling and resource utilization will always take place regardless of the SS7 information known on the termination side. So, for example, if a termination switch does not have resources to complete the phone call, the VoIP network will still use resources all along the call path to setup the call, and then use resources to tear down the call once it finds out that the termination switch cannot take the call. Therefore, the resources in the VoIP network are wasted if the call setup is not successful in the termination leg.
Therefore, there exists a need for a call setup method in which the H.323 call setup does not start if the termination leg cannot take the call.
Additionally, the SS7 signaling is usually faster than the H.323 signaling. Therefore the use of H.323 signaling adds to call setup time. Thus, there also exists a need in the art for a system that can execute the SS7 call setup faster than in present day art, without having to experience delays associated with traversing the IP network and execution the H.323 protocol.